This invention relates generally to construction vehicles commonly referred to as tractor-loader-backhoes and, more particularly, to a tapered pivot pin mount for the loader mechanism, an improved transport lock for the backhoe, and an improved backhoe boom construction.
Loader mechanisms are pivotally mounted to the frame of a prime mover to be operable forwardly of the tractor-loader-backhoe, commonly referred to as a TLB. This pivotal mounting of the loader mechanism is typically accomplished by use of a tapered pivot pin that would typically be supported in a conical hub forming part of the frame of the prime mover. The tapered pivot pin would be fastened to the frame of the prime mover by a short bolt threaded into the pin to seat the tapered pin into the conical hub. The clamp load exerted by this fastener does not consistently seat the tapered pin into the conical hub permitting the pin to loosen, and, as a result, induce failure to the pivot pin, thereby destroying the pivotal mounting of the loader mechanism to the prime mover.
Backhoe mechanisms are pivotally mounted to the rear of the frame of the prime mover to permit swinging movement about a generally vertical axis, as well as articulated movement of the boom assembly itself within a vertical plane. The transportation of the TLB from one job site to another requires a fixing of the backhoe boom assembly in a rearwardly extending position generally aligned with the center line of the prime mover, although the articulated movement of the boom assembly would be compacted to limit the overall length of the machine. To fix the boom assembly into this transport position, the TLB would incorporate a transport lock utilizing a shear plate to fit within a slot on the portion of the prime mover frame carrying the generally vertical pivot axis for the backhoe boom assembly. It has been found on occasion that the shear plate would not properly operate resulting in a failure of the swing post casting forming a portion of the prime mover frame, which is a very expensive and difficult part to replace.
Construction of the boom assembly in prior art backhoe mechanisms typically utilized a box beam construction or perhaps C-channel members which are butt welded to form the boom member and dipper member portions of the boom assembly. Because of the heavy bending and torsional loads induced into the boom assembly during operation of the backhoe, it has been necessary to construct the boom member and dipper member with substantially sized members having relatively heavy wall thicknesses to withstand the operating loads induced therein. Furthermore, the butt welding of members requires finely cut edges to assure a proper welding therebetween. Such construction results in a greater expense due to the care of maintaining weldable edges. It would be desirable to provide a method of constructing the boom and dipper members of a backhoe mechanism which is lighter, more rapidly formed and more conducive to welding, without sacrificing structural strength or integrity.